# Specifying Buffer Calculations - MapInfo_Pro - 2023

## MapInfo Pro Help

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2023
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MapInfo Pro
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MapInfo Pro Help
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1985
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2023-09-12
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2023-09-12T16:39:16.995549

To specify buffer calculations:

1. On the SPATIAL tab, in the Edit group, click Buffer Objects fro the list to open the Buffer Objects dialog box.
2. Check one of the following:

Spherical: Spherical calculations are used for distance methods that attempt to keep the measurement on the curved surface of the earth. The data is first converted to Latitude/Longitude and then a calculation is produced. Non-earth data cannot use Spherical calculations, since the data cannot be converted to Latitude/Longitude.

Cartesian: Cartesian methods are used to perform calculations on Non-earth data. Cartesian coordinates are a pair of numbers, (x, y), defining the position of a point in two-dimensional space by its perpendicular projection onto two axes that are at right angles to each other. Cartesian calculations cannot be used for Latitude/Longitude data, which is not a flat projection.

Note: The only calculations available for the target table's projections are those that will produce a valid result. For example, Cartesian is not available for a Latitude/Longitude projection because it cannot be used on a curved surface. Spherical is not available for a table in a non-earth projection it is not curved, and cannot be converted to Latitude/Longitude.
3. Click OK.

Displaying Distance, Length, Perimeter, and Area Calculations

Changing the Default or Preference Setting for Calculations

## Convex Hull Buffers

The Convex Hull command provides another means of creating a polygon around a selected object or objects. Convex Hull is similar to creating a buffer in several ways. Like a buffer, the Convex Hull command always creates an object from the input objects, and it will place the result objects into the editable layer. In addition, you have a choice to create one convex hull object from all of the input objects, or to create one convex hull object for each input object.

The resulting region object(s) are based on the nodes from the input object. The Convex Hull command can be thought of as an operator that places a rubber band around all of the points. It consists of a minimal set of points such that all other points lie on or inside the polygon. Since the polygon is convex, no interior angles are greater than 180 degrees. No attribute data is aggregated in this operation. To use Convex Hull, a Map window must be active, it must have an editable layer, and objects in the editable layer must be selected.

To create convex hull objects:

1. On the SPATIAL tab, in the Edit group, click Convex Hull to open the Create Convex Hull dialog box.
2. Select the type of convex hull objects you want to create. You have two options:
• One output object for all input objects button is the default setting. It creates one convex hull object around all of the selected objects.
• One output object for each input object button creates a convex hull object around each selected object.
3. Click OK.

Your map redisplays. The convex hull object(s) is displayed over the input objects. If you want to save this data, save the editable table. The convex hull object is selected when it displays.

4. To change the fill of the convex hull object, do one of the following:
• Double-click it to open the Region Object dialog box. Click the Style icon at the bottom of the dialog box to open the Region Style dialog box. Make any changes you like and click OK.
• Select the convex hull object, if it is not already. On the SPATIAL tab, in the Create group, on the Style list, click Region Style from the list to open the Region Style dialog box. Make the changes you want and click OK.